It is well known that materials which are thought of as transparent do, in fact, reflect some light. Therefore, glass and other transparent materials are capable of producing glare. Traditionally, transmission screens, such as television screens, have been made from glass or some other similar transparent material. As a result, a good deal of glare may be encountered in a desired viewing area due to ambient light striking the front face of the transmission screen and being reflected. For example, glare can be an especially annoying problem when viewing a television screen in a brightly lit room or when sunlight impinges on the screen.
Prior attempts have been made to eliminate or reduce undesired glare from transmission screens, such as television screens. For instance, the glare problem has been reduced by increasing the intensity of radiation from the television tube. But this, in turn, has increased the cost of the television.
Another attempted solution to the glare problem associated with television screens is disclosed in U.S. Pat. No. 2,909,770, where the front surface of the television screen is provided with a series of parallel grooves. The grooves have alternately intersecting surfaces, one ofwhich is coated with a black or light-absorbing substance, such as dull black paint, and the other of which is reflective and tilted so that ambient light can be reflected onto the light-absorbing surface and not to the desired viewing area of the television screen. However, because the screen itself must be first grooved and then coated, in specific areas, with a light-absorbing material, such as screen would be extremely difficult and expensive to manufacture.
In FIG. 1 of my U.S. Pat. No. 4,165,920, there is shown an overlay adapted for direct attachment to the viewing surface of a transmission screen, such as a television screen or an instrumentation display of an airplane. The overlay reduces front-face glare by providing the front face of the overlay with a plurality of parallel, generally horizontal ridges. Each ridge is formed from a generally horizontal surface which cooperates with an inclined surface to form a peak. The inclined surface of each ridge is arranged at a preselected angle relative to the horizontal, the angle being selected such that ambient light in front of the overlay is deflected downwardly away from the viewing area. It was found, however, that when utilizing such an overlay, the problem of echos or ghost images is created due, at least in part, to the reflection of light from the transmission screen off of the horizontal surfaces of the ridges.
Also disclosed in my U.S. Pat. No. 4,165,920 is an anti-glare overlay (see FIG. 4) which was designed to overcome the above-described echo problem. The overlay of FIG. 4 is essentially identical to the overlay of FIG. 1 except that in the overlay of FIG. 4 a coating of opaque material is applied to the upper portion of the inclined surface of each ridge to eliminate an echo of the image being viewed by blocking the transmission of the echo image reflected off of the horizontal surface of an associated ridge. In practice, it has proven difficult to apply the opaque material to the peaks of the inclined surfaces. It has also proven difficult to manufacture the peaks with a sharp point. Because the peaks therefore have a round or lenticular shape which is difficult to coat with an opaque material, light from the transmission screen is refracted by the uncoated or partially coated peaks in a number of different vertical directions, thereby creating a further echo problem.